1.修改系統(tǒng)音量 MPVolumeView 系統(tǒng)提供的音量控件，它里面的MPVolumeSlider是私有的? 但是可以獲取它來改變他的value從而修改音量，如果不想要系統(tǒng)的音量改變的提示框，可以把MPVolumeView放在屏幕外面

?MPVolumeView*volumeView = [[MPVolumeViewalloc]init];

[self.viewaddSubview:volumeView];

UISlider* volumeViewSlider =nil;

for(UIView*viewin[volumeViewsubviews]){

if([view.class.descriptionisEqualToString:@"MPVolumeSlider"]){

volumeViewSlider = (UISlider*)view;

break;??????? }

}

floatsystemVolume = volumeViewSlider.value;

[volumeViewSlidersetValue:1.0fanimated:NO];

_volumeViewSlider= volumeViewSlider;

?[volumeViewSlider sendActionsForControlEvents:UIControlEventTouchUpInside];

2.監(jiān)聽系統(tǒng)音量的改變

NSError *error;

?[[NSNotificationCenter defaultCenter] addObserver:self???????????????????????????????????????????????? selector:@selector(volumeChanged:)???????????????????????????????????????????????????? name:@"AVSystemController_SystemVolumeDidChangeNotification"?????????????????????????????????????????????????? object:nil];

[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];//注，ios9上不加這一句會無效，加了這一句后，

//在移除通知時(shí)候加上這句[[UIApplication sharedApplication] endReceivingRemoteControlEvents];

-(void)volumeChanged:(NSNotification *)noti{

float volume =?????? [[[noti userInfo]?????????? objectForKey:@"AVSystemController_AudioVolumeNotificationParameter"]???????? floatValue];

NSLog(@"volumn is %f", volume);

}